[BUG] Incorrect PRF declared and used in KDF for ciphersuites A256GCM and AES-CCM-64-128-256

[Sai-Anudeep47]

To simplify issue resolution process, please provide network logs, and or test voucher.

What part of the spec are you testing?

• [ ] Rendezvous Server
• [ ] Device Onboarding Service
• [x] Device Implementation

What protocol are having issue with?

• [ ] TO0
• [ ] TO1
• [x] TO2

Issue description

• The PRF / HMAC used in KDF for cipher suites A256GCM and AES-CCM-64-128-256 is not accordance in spec as mentioned at https://tinyurl.com/ciphersuitesprf
• It is observed that HMAC-SHA384 is used on conformance owner (https://github.com/fido-alliance/fdo-fido-conformance-server/blob/main/core/shared/enc.crypto.go#L86) for the mentioned ciphers instead of HMAC-SHA256 as provided in spec link.
• This is also resulting in generating incorrect keys for encryption and decryption related to #46
• Screenshots are attached for reference.

[yackermann]

Good catch @Sai-Anudeep47